The production of various thin-walled tubes and sleeves requires that the normally cast workpiece be held accurately while its surfaces are ground or even superfinished, in particular the end faces of bushings. Such workpieces, in addition to being fairly flexible, also often have complexly shaped outside surfaces, as for instance when used as seals or bearing parts, presenting another obstacle to gripping them.
The problem is that the holder or chuck should not deform the workpieces, while at the same time it should hold them so solidly that they do not move inappropriately while being machined. This is particularly difficult with such workpieces when their outside surfaces are irregular and often unfinished as a result of the casting. Obviously these problems are all compounded by the fact that the items in question are mass produced in large volume, but must still conform to relatively tight tolerances.